Electron Source Architecture for a Scanning Electron Microscopy System

ABSTRACT

A scanning electron microscopy (SEM) system includes a plurality of electron-optical columns and a plurality of electron beam sources. The electron beam sources include an emitter including one or more emitter tips configured to generate one or more electron beams of a plurality of electron beams. The electron beam sources include a stack of one or more positioners configured to adjust a position of the emitter based on one or more measurements of the electron beam generated by the emitter. The emitter is configured to scan the one or more electron beams across an area surrounding a bore of an electron-optical column of the plurality of electron-optical columns. The electron beam source array includes a carrier plate and a source tower. The source tower is configured to adjust a position of the plurality of electron beam sources relative to a position of the plurality of electron-optical columns.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit under 35 U.S.C. § 119(e) ofU.S. Provisional Patent Application Ser. No. 62/455,961, filed Feb. 7,2017, entitled ELECTRON SOURCE ARCHITECTURE FOR A MULTI-EMITTERMULTI-COLUMN ELECTRON OPTICS, naming Mohammed Tahmassebpur as inventors,which is incorporated herein by reference in the entirety.

TECHNICAL FIELD

The present invention generally relates to wafer and photomask/reticlecharacterization and fabrication and, more particularly, to an electronsource architecture for a scanning electron microscopy system.

BACKGROUND

The fabrication of semiconductor devices, such as logic and memorydevices, typically includes processing a semiconductor device using alarge number of semiconductor fabrication and metrology processes toform various features and multiple layers of the semiconductor devices.Select fabrication processes utilize photomasks/reticles to printfeatures on a semiconductor device such as a wafer. As semiconductordevices become smaller and smaller laterally and extended vertically, itbecomes critical to develop enhanced inspection and review devices andprocedures to increase sensitivity and throughput of photomask, reticle,and wafer inspection processes.

One inspection technology includes electron beam-based inspection suchas scanning electron microscopy (SEM). In some instances, scanningelectron microscopy is performed via secondary electron beam collection(e.g., a secondary electron (SE) imaging system). In other instances,scanning electron microscopy is performed by splitting a single electronbeam into numerous beams and utilizing a single electron-optical columnto individually tune and scan the numerous beams (e.g., a multi-beam SEMsystem). In other instances, scanning electron microscopy is performedvia an SEM system which includes an increased number of electron-opticalcolumns (e.g., a multi-column SEM system).

SEM systems include electron beam sources that generate electron beamsutilized to characterize a photomask/reticle or wafer. Traditionally,the electron beam sources each include an electron emitter with anemitter tip. When an emitter tip burns out, all electron beam sourcesmust be removed from the SEM system. Where the electron beam sources arecoupled together in a single assembly, the ultra-high vacuum (UHV)environment in which the SEM system operates must be broken so theburnt-out tip may be replaced. Repairing the burnt-out electron beamsource, reinstalling the electron beam source, and restoring the UHVenvironment may result in a downtime measured in weeks and repair costsmeasured in the tens of thousands of dollars.

The electron beams generated by the electron beam sources are extremelysensitive to misalignment, to the order of microns, such thatmisalignment may occur from improper installation of the electron beamsources, system jitter, emitter tip expansion when heated, or the like.To correct for the misalignment, each electron emitter of an electronbeam source is coupled to a stack of positioners. The stack ofpositioners is manually adjusted from the atmospheric side of the UHV toprevent the breaking of the UHV. The manual adjustment is monitored viavisual or emission feedback and can be lengthy in time and/or tedious innature. In addition, the manual alignment is completed on a per-emitterbasis, and does not allow for the simultaneous alignment of multipleemitters. Further, the manual alignment when the SEM system is notoperational may be negated at least in part by the expansion of a heatedemitter tip when the SEM system is operational. This, combined with thesensitivity of the stack of positioners to the heat generated by theemitter tip during operation, causes considerable difficulty withaligning the electron beams.

Therefore, it would be advantageous to provide a system and method thatcures the shortcomings described above.

SUMMARY

A scanning electron microscopy (SEM) system is disclosed, in accordancewith one or more embodiments of the present disclosure. In oneembodiment, the SEM system includes an electron-optical column array. Inanother embodiment, the electron-optical column array includes aplurality of electron-optical columns. In another embodiment, the SEMsystem includes an electron beam source array couplable to theelectron-optical column array. In another embodiment, the electron beamsource array includes a plurality of electron beam sources configured togenerate a plurality of electron beams. In another embodiment, at leastsome of the electron beam sources include an emitter coupled to anemitter holder. In another embodiment, the emitter includes one or moreemitter tips configured to generate one or more electron beams of theplurality of electron beams. In another embodiment, the at least some ofthe electron beam sources include a stack of one or more positionerscoupled to the emitter holder. In another embodiment, the stack of oneor more positioners is configured to adjust a position of the emitterbased on one or more measurements of the electron beam generated by theemitter. In another embodiment, the emitter is configured to scan theone or more electron beams across an area surrounding a bore of aparticular electron-optical column of the plurality of electron-opticalcolumns. In another embodiment, the electron beam source array includesa carrier plate coupled to the plurality of electron beam sources. Inanother embodiment, the electron beam source array includes a sourcetower coupled to the carrier plate. In another embodiment, the sourcetower is configured to adjust a position of the plurality of electronbeam sources relative to a position of the plurality of electron-opticalcolumns.

A scanning electron microscopy (SEM) system is disclosed, in accordancewith one or more embodiments of the present disclosure. In oneembodiment, the SEM system includes an electron-optical column array. Inanother embodiment, the electron-optical column array includes aplurality of electron-optical columns. In another embodiment, the SEMsystem includes an electron beam source array couplable to theelectron-optical column array. In another embodiment, the electron beamsource array includes a plurality of electron beam sources configured togenerate a plurality of electron beams. In another embodiment, at leastsome of the electron beam sources include an emitter coupled to anemitter holder. In another embodiment, the emitter includes one or moreemitters tips configured to generate one or more electron beams of theplurality of electron beams. In another embodiment the at least some ofthe electron beam sources include a stack of one or more actuatorscoupled to the emitter holder. In another embodiment, the stack of oneor more actuators is configured to adjust a position of the emitter. Inanother embodiment, the at least some of the electron beam sourcesinclude a thermal bypass. In another embodiment, the thermal bypass ispositioned between the emitter holder and the stack of one or morepositioners. In another embodiment, the thermal bypass is positionedbetween the stack of one or more positioners and the carrier plate. Inanother embodiment, the thermal bypass is configured to transfer heatfrom the emitter holder to the carrier plate.

A scanning electron microscopy (SEM) system is disclosed, in accordancewith one or more embodiments of the present disclosure. In oneembodiment, the SEM system includes an electron-optical column array. Inanother embodiment, the electron-optical column array includes aplurality of electron-optical columns. In another embodiment, the SEMsystem includes an electron beam source array couplable to theelectron-optical column array. In another embodiment, the electron beamsource array includes a plurality of electron beam sources configured togenerate a plurality of electron beams. In another embodiment, at leastsome of the electron beam sources include an emitter. In anotherembodiment, the emitter includes a first emitter tip configured togenerate a first electron beam of the plurality of electron beams and asecond emitter tip configured to generate a second electron beam of theplurality of electron beams. In another embodiment, the second emittertip is configured to receive a selected amount of electric current whenthe first emitter tip fails.

A method is disclosed, in accordance with one or more embodiments of thepresent disclosure. In one embodiment, the method may include, but isnot limited to, scanning an area surrounding a bore of anelectron-optical element of an electron-optical column for an electriccurrent generated by an electron beam directed at the bore. In anotherembodiment, the electron-optical column is a component of anelectron-optical column array. In another embodiment, the method mayinclude, but is not limited to, determining coarse adjustment data basedon the scanned electric current. In another embodiment, the method mayinclude, but is not limited to, providing the coarse adjustment data toadjust a source tower of an electron beam source array via one or morecoarse alignment processes. In another embodiment, the method mayinclude, but is not limited to, determining fine adjustment data basedon the scanned electric current. In another embodiment, the method mayinclude, but is not limited to, providing the fine adjustment data toadjust one or more positioners coupled to an electron beam source of theelectron beam source array via one or more fine alignment processes. Inanother embodiment, at least one of the electron-optical column array orthe electron beam source array is a component of a scanning electronmicroscopy (SEM) system.

A method is disclosed, in accordance with one or more embodiments of thepresent disclosure. In one embodiment, the method may include, but isnot limited to, dismounting an electron beam source array from anelectron-optical column array. In another embodiment, the electron beamsource array includes a plurality of electron beam sources. In anotherembodiment, the plurality of electron beam sources generates a pluralityof electron beams. In another embodiment, the method may include, but isnot limited to, aligning a first electron beam source of the pluralityof electron beam sources with a viewport of a test chamber. In anotherembodiment, the first electron beam source generates a first electronbeam of the plurality of electron beams. In another embodiment, themethod may include, but is not limited to, performing one or moreinspection processes on the first electron beam of the plurality ofelectron beams. In another embodiment, the method may include, but isnot limited to, repositioning the first electron beam source within theelectron beam source array. In another embodiment, the method mayinclude, but is not limited to, aligning at least an additional electronbeam source of the electron beam source array with the viewport of thetest chamber. In another embodiment, the at least the additionalelectron beam source generates at least an additional electron beam ofthe plurality of electron beams. In another embodiment, the method mayinclude, but is not limited to, performing one or more inspectionprocesses on the at least the additional electron beam of the pluralityof electron beams. In another embodiment, the method may include, but isnot limited to, repositioning the at least the additional electron beamsource within the electron beam source array. In another embodiment, themethod may include, but is not limited to, remounting the electron beamsource array onto the electron-optical column array. In anotherembodiment, at least one of the electron beam source array, theelectron-optical column array, or the test chamber is a component of ascanning electron microscopy (SEM) system.

BRIEF DESCRIPTION OF THE DRAWINGS

The numerous advantages of the disclosure may be better understood bythose skilled in the art by reference to the accompanying figures inwhich:

FIG. 1A illustrates a simplified block diagram of a scanning electronmicroscopy (SEM) review tool including an electron beam source assembly,in accordance with one or more embodiments of the present disclosure;

FIG. 1B illustrates a simplified schematic view of an electron beamsource for an SEM review tool, in accordance with one or moreembodiments of the present disclosure;

FIG. 1C illustrates a simplified schematic view of an electron beamsource array for an SEM review tool, in accordance with one or moreembodiments of the present disclosure;

FIG. 1D illustrates a simplified schematic view of an electron beamsource array for an SEM review tool, in accordance with one or moreembodiments of the present disclosure;

FIG. 1E illustrates a simplified schematic view of an SEM review toolincluding multiple electron beam sources, in accordance with one or moreembodiments of the present disclosure;

FIG. 1F illustrates a simplified block diagram of an electron-opticalcolumn of an SEM review tool, in accordance with one or more embodimentsof the present disclosure;

FIG. 2 illustrates a simplified schematic view of a characterizationsystem including a controller, in accordance with one or moreembodiments of the present disclosure;

FIG. 3A illustrates a simplified schematic view of an SEM review tooltest chamber including a viewport for inspecting electron beams, inaccordance with one or more embodiments of the present disclosure;

FIG. 3B illustrates a simplified schematic view of an SEM review tooltest chamber including a viewport for inspecting electron beams, inaccordance with one or more embodiments of the present disclosure;

FIG. 3C illustrates a simplified schematic view of an SEM review tooltest chamber including a viewport for inspecting electron beams, inaccordance with one or more embodiments of the present disclosure;

FIG. 3D illustrates a simplified schematic view of an SEM review tooltest chamber including a viewport for inspecting electron beams, inaccordance with one or more embodiments of the present disclosure;

FIG. 3E illustrates a simplified schematic view of an SEM review tooltest chamber including a viewport for inspecting electron beams, inaccordance with one or more embodiments of the present disclosure;

FIG. 4A illustrates a process flow diagram depicting a method forcalibrating an electron beam in an SEM review tool, in accordance withone or more embodiments of the present disclosure; and

FIG. 4B illustrates a process flow diagram depicting a method forinspecting a source electron beam array of an SEM review tool, inaccordance with one or more embodiments of the present disclosure.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the subject matter disclosed,which is illustrated in the accompanying drawings.

Referring generally to FIGS. 1A-4B, an electron source architecture fora scanning electron microscopy (SEM) system is disclosed, in accordancewith one or more embodiments of the present disclosure.

Embodiments of the present disclosure are directed to a multi-emitter,multi-column scanning electron microscopy (SEM) tool. Embodiments of thepresent disclosure are also directed to wafer inspection or lithographyvia high brightness emission for electron-optical columns in themulti-column SEM tool. Embodiments of the present disclosure are alsodirected to automated alignment of an electron beam through a columnaperture or extractor bore of an electron-optical column. Embodiments ofthe present disclosure are also directed to in-situ visual, thermal,and/or vibration inspection of individual or group electron beam sourceswithin an electron beam source array. Embodiments of the presentdisclosure are also directed to in-situ calibration of individual orgroup electron beam sources within an electron beam source array.

FIGS. 1A-1F generally illustrate a scanning electron microscopy (SEM)review tool 100, in accordance with one or more embodiments of thepresent disclosure. It is noted herein that “SEM system” and “SEM reviewtool” may be considered synonymous for purposes of the presentdisclosure.

FIG. 1A illustrates a simplified block diagram of the SEM review tool100, in accordance with one or more embodiments of the presentdisclosure. FIG. 1B illustrates a simplified schematic view of anelectron beam source 104 of the SEM review tool 100, in accordance withone or more embodiments of the present disclosure.

In one embodiment, the SEM review tool 100 includes an electron beamsource array 102. In another embodiment, the electron beam source array102 includes one or more electron beam sources 104. In anotherembodiment, each electron beam source 104 includes an electron beamemitter 106. For example, the electron beam emitter 106 may include, butis not limited to, a Schottky emitter device, a carbon nanotube (CNT)emitter, a nanostructured carbon film emitter, a Muller-type emitter, orthe like. In another embodiment, each electron beam emitter 106 includesone or more emitter tips 108. For example, the electron beam emitter 106may include a single emitter tip 108. By way of another example, theelectron beam emitter 106 may include two emitter tips 108. By way ofanother example, the electron beam emitter 106 may include three or moreemitter tips 108. It is noted herein a particular electron beam emitter106 may include any number of emitter tips 108 that may fit within thespace dictated by the design of the electron beam emitter 106.

In another embodiment, the electron beam emitter 106 is coupled to anemitter holder 110. For example, the electron beam emitter 106 may becoupled to the emitter holder 110 via one or more clamp assemblies 112.For instance, the one or more clamp assemblies 112 may include, but arenot limited to, one or more standard clamp assemblies, one or morebrazed clamp assemblies, or the like. In another embodiment, the emitterholder 110 includes a high-voltage terminal 114. For example, thehigh-voltage terminal 114 may be coupled to one or more high-voltagewires. For instance, the high-voltage terminal 114 may be coupled tothree high-voltage wires.

In another embodiment, the electron beam emitter 106 is coupled to theone or more high-voltage wires. For example, where there are two emittertips 108 within the electron beam emitter 106, each emitter tip 108 maybe coupled to the one or more high-voltage wires. In this example,either one or both emitter tips 108 may be supplied with a current. Forinstance, the current may be supplied to a first emitter tip 108 of thetwo emitter tips, and then to a second emitter tip 108 of the twoemitter tips 108 after the first emitter tip 108 is non-operational(e.g., burns out). When the current is supplied to the second emittertip 108, the electron beam source 104 may be adjusted to align thesecond emitter tip 108. In this regard, the electron beam source 104 mayinclude a redundant emitter tip 108 arrangement, which may extend thelife of the electron beam source array 102. In addition, the emitter 106driving voltages and currents may be independently set and/or calibrateddue to the separate voltage pathways.

In another embodiment, the emitter holder 110 is coupled to a stack ofone or more positioners 116. In another embodiment, the stack of one ormore positioners 116 is configured to actuate the emitter holder 110(and the electron beam emitter 106) in one or more directions. Forexample, the stack of one or more positioners 116 may translate theemitter holder 110 (and the electron beam emitter 106) in one or more ofan x-direction, a y-direction, or a z-direction (e.g., along an x-axis,a y-axis, and/or a z-axis). By way of another example, the stack of oneor more positioners 116 may rotate the emitter holder 110 (and theelectron beam emitter 106) in a rotational direction around an axis(e.g., a rotational direction around an x-axis, a y-axis, and/or az-axis). In another embodiment, the stack of one or more positioners 116is configured to move the emitter holder 110 (and the electron beamemitter 106) independently to the required target position from otherstacks of one or more positioners 116 within the electron beam sourcearray 102. It is noted herein, however, that a stack of one or morepositioners 116 may be configured to actuate multiple electron beamsources 104 of the electron beam source array 102 either as a partialunit grouping together at least some of the multiple electron beamsources 104 or as a complete unit grouping together all of the multipleelectron beam sources 104. Therefore, the above description should notbe interpreted as a limitation on the scope of the present disclosurebut merely an illustration.

In another embodiment, the stack of one or more positioners 116 isconfigured to operate in an ultra-high vacuum (UHV) environment. Inanother embodiment, the stack of one or more positioners 116 isconfigured to provide feedback. For example, the feedback may begenerated via resistive and/or capacitive encoders positioned within theUHV environment. By way of another example, the feedback may be optical(e.g., via a viewport or via an optical interferometer).

In another embodiment, a heated emitter tip 108 generates heat,operating at a selected temperature (e.g., the heated emitter tip 108may operate at approximately 1800K). In another embodiment, the stack ofone or more positioners 116 is sensitive to the generated heat. Forexample, the excess heat may damage the stack of one or more positioners116, rendering them unusable. In another embodiment, the electron beamsource 104 includes one or more thermal bypasses 118. For example, theone or more thermal bypasses 118 are positioned between the emitterholder 110 and the stack of one or more positioners 116. In this regard,the one or more thermal bypasses 118 transfer heat away from the stackof one or more positioners 116, such that heat generated by a heatedemitter tip 108 may not interfere and/or otherwise damage the stack ofone or more positioners 116.

In another embodiment, the electron beam source array 102 includes acarrier plate 120. In another embodiment, the stack of one or morepositioners 116 is coupled to the carrier plate 120. In anotherembodiment, the electron beam source array 102 includes a magneticshield 122. For example, the magnetic shield 122 may be a component ofthe electron beam source array 102 surrounding the electron beam sources104. By way of another example, the magnetic shield 122 may be builtwithin each electron beam source 104.

In another embodiment, the electron beam source array 102 includes asource tower 124. In another embodiment, the source tower 124 providesposition adjustment to the electron beam sources 104 via one or morexyz-manipulators, or actuators, 126. For example, the one or moreactuators 126 may translate the electron beam sources 104 in one or moreof an x-direction, a y-direction, or a z-direction (e.g., along anx-axis, a y-axis, and/or a z-axis). For instance, the one or moreactuators 126 may re-position (e.g., raise or lower) the electron beamsources 104 during inspection, adjustment, and/or calibration of theelectron beam sources 104. By way of another example, the one or moreactuators 126 may rotate the electron beam sources 104 (and thus theelectron beam emitter 106) in a rotational direction around an axis(e.g., a rotational direction around an x-axis, a y-axis, and/or az-axis).

In another embodiment, where the magnetic shield 122 in a component ofthe electron beam source array 102 surrounding the electron beam sources104, the source tower 124 is coupled to the magnetic shield 122 via aflexible joint 128. For example, the flexible joint 128 may provide apressure force between the magnetic shield 122 and the source tower 124.By way of another example, the flexible joint 128 by include, but is notlimited to, a spring.

Although embodiments of the present disclosure are directed to the SEMreview tool 100 including primary adjustment capabilities via the stackof one or more positioners 116 and secondary adjustment capabilities viathe one or more actuators 126, it is noted herein the SEM review tool100 may only include the primary adjustment capabilities via the stackof one or more positioners 116. Therefore, the above description shouldnot be interpreted as a limitation on the scope of the presentdisclosure but merely an illustration.

In another embodiment, the one or more thermal bypasses 118 transferheat from the emitter holder 110 to the carrier plate 120. In anotherembodiment, the one or more thermal bypasses 118 transfer heat from theemitter holder 110 to the magnetic shield 122. In another embodiment,the one or more thermal bypasses 118 transfer heat from the emitterholder 110 to the source tower 124. In this regard, heat may betransferred around the stack of one or more positioners 116, effectivelybypassing the stack of one or more positioners 116.

FIGS. 1C and 1D generally illustrate a simplified schematic view of anelectron beam source array 102, in accordance with one or moreembodiments of the present disclosure.

In one embodiment, the electron beam source array 102 includes one ormore electron beam sources 104. For example, as illustrated in FIG. 1C,the electron beam source array 102 may include, but is not limited to,sixteen electron beam sources 104 arranged in a 4×4 array. By way ofanother example, the electron beam source array 102 may include, but isnot limited to, twenty-four electron beam sources 104 arranged in a 6×4array. In another embodiment, each electron beam source 104 of theelectron beam source array 102 includes one or more emitter holes. Forexample, as illustrated in FIG. 1C, the electron beam source 104 mayinclude, but is not limited to, emitter hole 106 a in the emitter 106for a single emitter tip 108. By way of another example, as illustratedin FIG. 1D, the electron beam source 104 may include, but is not limitedto, emitter holes 106 a and 106 b in the emitter 106 for two emittertips 108.

In another embodiment, each of the one or more electron beam sources 104in the electron beam source array 102 includes an emitter holder 110coupled to the emitter 106. In another embodiment, each of the one ormore electron beam sources 104 in the electron beam source array 102includes a stack of one or more positioners 116 coupled to the emitterholder 110. In another embodiment, each of the one or more electron beamsources 104 in the electron beam source array 102 includes a thermalbypass 118 surrounding the stack of one or more positioners 116. Inanother embodiment, the electron beam source array 102 includes thecarrier plate 120. In another embodiment, the carrier plate 120 includesone or more components of one or more kinematic mount assemblies 134.

Referring again to FIG. 1A, in one embodiment the electron beam sourcearray 102 is mechanically aligned to an electron-optical column array130 including one or more electron-optical columns 132 via the one ormore kinematic mount assemblies 134, where the kinematic mountassemblies 134 allow for repeatable positioning of the electron beamsource array 102 on the electron-optical column array 130. For example,one or more kinematic mount assemblies 134 may include a ball-and-grooveassembly. By way of another example, the carrier plate 120 and theelectron-optical column array 130 may be mechanically aligned via threekinematic mount assemblies 134. For instance, the three kinematic mountassemblies 134 may be arranged at 120-degree intervals around asubstantially circular carrier plate 120. In another embodiment, thekinematic mount assemblies 134 include one or more safety switches,where the safety switches indicate misalignment and/or allow or preventthe operation of the electron beam source array 102. For example, theone or more safety switches may be electrical. For instance, eachkinematic mount assembly 134 may include two electrical safety switches,where not completing the circuit in either or both of the two electricalsafety switches prevents the electron beam source array 102 fromoperating.

In another embodiment, the source tower 124 is configured to adjust aposition of the one or more electron beam sources 104 relative to aposition of the one or more electron-optical columns 132 based onfeedback from the one or more kinematic mount assemblies 134 along oraround at least one of an x-axis, a y-axis, or a z-axis. In anotherembodiment, the source tower 124 is configured to adjust a position ofthe one or more electron beam sources 104 relative to a position of theone or more electron-optical columns 132 based on feedback from the oneor more safety switches of the one or more kinematic mount assemblies134 along or around at least one of an x-axis, a y-axis, or a z-axis.

In another embodiment, the SEM review tool 100 operates in an ultra-highvacuum (UHV) environment. In another embodiment, the electron beamsource array 102 and/or the electron-optical column array 130 areconstructed from components treated and/or designed for usage in a UHVenvironment. For example, one or more components of the electron beamsource array 102 (e.g., the electron beam emitters 106) and/or theelectron-optical column array 130 may include ports for the UHVenvironment. By way of another example, components are treated for usagein the UHV environment by being cleaned and baked, then installed in theSEM review tool 100, then baked again in the constructed form. Forinstance, the SEM review tool 100 may include soft wires, where the softwires include silver conductors with a clean and baked polyamide thincoating. It is noted herein the soft wires are selected for the SEMreview tool 110 so as to not damage the stack of one or more positioners116.

In another embodiment, the SEM review tool 100 includes one or morecomponents usable during operation in the UHV environment. For example,the SEM review tool 100 may include one or more sensors, wires,encoders, cables, or the like necessary to perform measurements and/oradjust components of the SEM review tool 100 while the SEM review tool100 is in operation. By way of another example, where the electron beamsource array 102 is a removable component (e.g., a field replacementunit) of the SEM review tool 100, the SEM review tool 100 may include avalve that seals the UHV environment, which allows for the removal ofthe electron beam source array 102 without breaking the UHV environmentof the electron-optical column array 130. In this regard, the downtimeand/or recalibration necessary when servicing or replacing the electronbeam source array 102 is greatly reduced, as the UHV environment doesnot need to be broken and rebuilt for the entire SEM review tool 100.

Although embodiments of the present disclosure are directed to anelectron beam source array 102 that is removeable from theelectron-optical column array 130 via the one or more kinematic mountassemblies 134, it is noted herein the electron beam source array 102may be permanently mounted to the electron-optical column array 130. Inaddition, although embodiments of the present disclosures are directedto an electron beam source array 102 including one or more electron beamsources 104 coupled to the electron-optical column array 130 includingthe one or more electron-optical columns 132, it is noted herein the SEMreview tool 100 may include complete miniature assemblies with a singleelectron beam source 104 coupled to a single electron-optical column132. Therefore, the above description should not be interpreted as alimitation on the scope of the present disclosure but merely anillustration.

In another embodiment, the one or more electron beam sources 104 includeone or more source electron-optical elements. For example, the one ormore source electron-optical elements may direct at least a portion ofan electron beam generated by the electron beam emitter 106 of anelectron beam source 104 to a particular electron-optical column 132 ofan electron-optical column array 130.

It is noted herein that the SEM review tool 100 may include any or allcomponents including, but not limited to, redundant emitter tips 108 inthe emitters 106 of the electron beam sources 104; an automated systemfor adjustment of stacks of one or more positioners 116 for the electronbeam sources 104; thermal bypasses 118 capping the stacks of one or morepositioners 116; magnetic shields 122 surrounding the electron beamsources 104; kinematic mount assemblies 134 between the electron beamsource array 102 and the electron-optical column array 130; and/orUHV-compliant fabrication components. In this regard, the SEM reviewtool 100 does not require any particular set of components as listedthroughout the embodiments herein. Therefore, the above descriptionshould not be interpreted as a limitation on the scope of the presentdisclosure but merely an illustration.

FIGS. 1E and 1F illustrate a simplified schematic view of an SEM reviewtool 100, in accordance with one or more embodiments of the presentdisclosure.

In one embodiment, the SEM review tool 100 is a multi-column SEM reviewtool 100. It is noted herein, however, that the SEM review tool 100 mayinclude, but is not limited to, a secondary electron (SE) review tool100, a multi-beam SEM review tool 100, or the like. Therefore, the abovedescription should not be interpreted as a limitation on the scope ofthe present disclosure but merely an illustration.

In another embodiment, the multi-column SEM review tool 100 includes theelectron-optical column array 130. In another embodiment, theelectron-optical column array 130 includes two or more electron-opticalcolumns 132. Although FIG. 1E illustrates two electron beam sources 104within the electron beam source array 102, it is noted herein that theSEM review tool 100 may include one electron beam source 104 perelectron-optical column 132. Therefore, the above description should notbe interpreted as a limitation on the scope of the present disclosurebut merely an illustration.

Referring now to FIG. 1F, in another embodiment the two or moreelectron-optical columns 132 each include one or more electron-opticalelements 140. For example, the one or more electron-optical elements 140may include, but are not limited to, one or more electrostatic lenses,one or more electromagnetic lenses, or the like. For instance, the oneor more electron-optical elements 140 may include, but are not limitedto, one or more apertures 142, one or more condenser lenses 144, one ormore beam deflectors 146 or scanning coils 146, one or more objectivelenses 148, or the like. By way of another example, the one or moreelectron-optical elements 140 include one or more electron detectors150. For instance, the one or more electron-optical elements 140 mayinclude, but are not limited to, one or more electron detectors 150positioned within the electron-optical column 132. In addition, the oneor more electron-optical elements 140 may include, but are not limitedto, one or more secondary electron detectors positioned outside theelectron-optical column 132 (e.g., outside at least one outer-ringelectron-optical column 132 where the electron-optical columns 132 ofthe electron-optical column array 130 are arranged in an outer ring andat least one inner ring).

In another embodiment, the electron beam source 104 generates anelectron beam 152. For example, where there are two or more electronbeam sources 104, the two or more electron beam sources 104 may generatean electron beam 152 specific to a particular electron-optical column132 of the electron-optical column array 130. By way of another example,where there are two or more electron beam sources 104, the two or moreelectron beam sources 104 may generate an electron beam 152 that issplit and/or directed to two or more electron-optical columns 132 of theelectron-optical column array 130 via one or more electron-opticalelements located between the two or more electron beam sources 104 andthe two or more electron-optical columns 132.

In another embodiment, the electron-optical column 132 directs at leasta portion of the electron beam 152 onto a sample 136 secured on a samplestage 138. In another embodiment, the sample 136 may backscatter, emit,radiate, and/or deflect one or more electrons 154 in response to theelectron beam 152. In another embodiment, the one or more electrondetectors 150 may detect the one or more electrons 154 backscattered,radiated, and/or deflected from the surface of the sample 136.

The sample 136 may include any sample suitable for inspection and/orreview. In one embodiment, the sample 136 includes a photomask/reticle,semiconductor wafer, or the like. As used through the presentdisclosure, the term “wafer” refers to a substrate formed of asemiconductor and/or a non-semiconductor material. For instance, in thecase of a semiconductor material, the wafer may be formed from, but isnot limited to, monocrystalline silicon, gallium arsenide, and/or indiumphosphide. As such, the term “wafer” and the term “sample” may be usedinterchangeably in the present disclosure. Therefore, the abovedescription should not be interpreted as a limitation on the scope ofthe present disclosure but merely an illustration.

It is noted herein that many different types of devices may be formed ona wafer, and the term wafer as used herein is intended to encompass awafer on which any type of device known in the art is being fabricated.Therefore, the above description should not be interpreted as alimitation on the scope of the present disclosure but merely anillustration.

The sample stage 138 may include any appropriate mechanical and/orrobotic assembly known in the art of electron beam microscopy. In oneembodiment, the sample stage 138 is an actuatable stage. For example,the sample stage 138 may include, but is not limited to, one or moretranslational stages suitable for selectively translating the sample 136along one or more linear directions (e.g., x-direction, y-direction,and/or z-direction). By way of another example, the sample stage 138 mayinclude, but is not limited to, one or more rotational stages suitablefor selectively rotating the sample 136 along a rotational direction. Byway of another example, the sample stage 138 may include, but is notlimited to, a rotational stage and a translational stage suitable forselectively translating the sample 136 along a linear direction and/orrotating the sample 136 along a rotational direction. By way of anotherexample, the sample stage 138 may be configured to translate or rotatethe sample 136 for positioning, focusing, and/or scanning in accordancewith a selected inspection or metrology algorithm, several of which areknown to the art.

Although embodiments of the present disclosure are directed to an SEMreview tool 100, it is noted herein any of the embodiments directed tothe SEM review tool 100 and/or components of the SEM review tool 100 maybe directed to a focused ion beam (FIB) review tool and/or components ofthe FIB review tool, for purposes of the present disclosure. Inaddition, it is noted herein any of the embodiments directed to the SEMreview tool 100 and/or components of the SEM review tool 100 may bedirected to any appropriate characterization tool known in the art. In ageneral sense, the characterization tool may include anycharacterization tool suitable for characterizing one or more samples,such as, but not limited to, photomasks/reticles, or wafers. Therefore,the above description should not be interpreted as a limitation on thescope of the present disclosure but merely an illustration.

Although embodiments of the present disclosure are directed to anelectron-based characterization tool (e.g., SEM review tool 100), it isnoted herein any of the embodiments directed to the SEM review tool 100and/or components of the SEM review tool 100 may be directed to acharacterization tool including an optical inspection tool. For example,the optical inspection tool may include an optical inspection toolcapable of operating at a wavelength corresponding to, but not limitedto, visible light, DUV radiation, UV radiation, VUV radiation, EUVradiation, and/or X-ray radiation.

FIG. 2 illustrates a characterization system 200 including acharacterization tool and a controller 202, in accordance with one ormore embodiments of the present disclosure.

In one embodiment, the characterization tool is the SEM review tool 100.In another embodiment, the controller 202 is operably coupled to one ormore components of the SEM review tool 100. For example, the controller202 may be operably coupled to the electron beam source array 102 and/orcomponents of the electron beam source array 102 (e.g., the one or moreelectron beam sources 104 including the stack of one or more positioners116, or the like), the electron-optical column assembly 130 and/orcomponents of the electron-optical column assembly 130 (e.g., the one ormore electron-optical columns 132 including electrostatic lenses,electromagnetic lenses, detectors, or the like), and/or the sample stage138. In this regard, the controller 202 may direct any of the componentsof the characterization tool 100 to carry out any one or more of thevarious functions described throughout the present disclosure.

In another embodiment, the controller 202 includes one or moreprocessors 204 and memory 206. In another embodiment, the memory 206stores a set of program instructions 208. In another embodiment, the setof program instructions 208 is configured to cause the one or moreprocessors 204 to carry out any of the one or more process stepsdescribed throughout the present disclosure.

The controller 202 may be configured to receive and/or acquire data orinformation from other systems or tools (e.g., one or more sets ofinformation from the electron beam source array 102 and/or components ofthe electron beam source array 102 including the one or more electronbeam sources 104 with the stack of one or more positioners 116, or thelike), the electron-optical column assembly 130 and/or components of theelectron-optical column assembly 130 (e.g., the one or moreelectron-optical columns 132 including electrostatic lenses,electromagnetic lenses, detectors, or the like), and/or the sample stage138) of the characterization tool 100 by a transmission medium that mayinclude wireline and/or wireless portions. In addition, the controller202 may be configured to transmit data or information (e.g., the outputof one or more procedures of the inventive concepts disclosed herein) toone or more systems or tools (e.g., one or more sets of information fromthe electron beam source array 102 and/or components of the electronbeam source array 102 with the one or more electron beam sources 104including the stack of one or more positioners 116, or the like), theelectron-optical column assembly 130 and/or components of theelectron-optical column assembly 130 (e.g., the one or moreelectron-optical columns 132 including electrostatic lenses,electromagnetic lenses, detectors, or the like, and/or the sample stage138) of the characterization tool 100 by a transmission medium that mayinclude wireline and/or wireless portions. In this regard, thetransmission medium may serve as a data link between the controller 202and the other subsystems of the characterization tool 100. In addition,the controller 202 may be configured to send data to external systemsvia a transmission medium (e.g., network connection).

The one or more processors 204 may include any one or more processingelements known in the art. In this sense, the one or more processors 204may include any microprocessor device configured to execute algorithmsand/or program instructions. For example, the one or more processors 204may consist of a desktop computer, mainframe computer system,workstation, image computer, parallel processor, handheld computer(e.g., tablet, smartphone, or phablet), or other computer system (e.g.,networked computer). In general, the term “processor” may be broadlydefined to encompass any device having one or more processing elements,which execute the set of program instructions 208 from a non-transitorymemory medium (e.g., the memory 206). Moreover, different subsystems ofthe characterization tool 100 (e.g., one or more sets of informationfrom the electron beam source array 102 and/or components of theelectron beam source array 102 including the one or more electron beamsources 104 with the stack of one or more positioners 116, or the like),the electron-optical column assembly 130 and/or components of theelectron-optical column assembly 130 (e.g., the one or moreelectron-optical columns 132 including electrostatic lenses,electromagnetic lenses, detectors, or the like, and/or the sample stage138) may include processor or logic elements suitable for carrying outat least a portion of the steps described throughout the presentdisclosure. Therefore, the above description should not be interpretedas a limitation on the present disclosure but merely an illustration.

The memory 206 may include any storage medium known in the art suitablefor storing the set of program instructions 208 executable by theassociated one or more processors 204. For example, the memory 206 mayinclude a non-transitory memory medium. For instance, the memory 206 mayinclude, but is not limited to, a read-only memory (ROM), a randomaccess memory (RAM), a magnetic or optical memory device (e.g., disk), amagnetic tape, a solid state drive, and the like. The memory 206 may beconfigured to provide display information to a display device of a userinterface. In addition, the memory 206 may be configured to store userinput information from a user input device of the user interface. Thememory 206 may be housed in a common controller 202 housing with the oneor more processors 204. The memory 206 may, alternatively or inaddition, be located remotely with respect to the spatial location ofthe processors 204 and/or the controller 202. For instance, the one ormore processors 204 and/or the controller 202 may access a remote memory206 (e.g., server), accessible through a network (e.g., internet,intranet, and the like).

In one embodiment, the characterization system 200 includes a userinterface. In another embodiment, the user interface is coupled to thecontroller 202 (e.g., physically coupled and/or communicativelycoupled). In another embodiment, the user interface includes a display.In another embodiment, the user interface includes a user input device.In another embodiment, the display device is coupled to the user inputdevice. For example, the display device may be coupled to the user inputdevice by a transmission medium that may include wireline and/orwireless portions.

The display device may include any display device known in the art. Forexample, the display device may include, but is not limited to, a liquidcrystal display (LCD). By way of another example, the display device mayinclude, but is not limited to, an organic light-emitting diode (OLED)based display. By way of another example, the display device mayinclude, but is not limited to a CRT display. Those skilled in the artshould recognize that a variety of display devices may be suitable forimplementation in the present invention and the particular choice ofdisplay device may depend on a variety of factors, including, but notlimited to, form factor, cost, and the like. In a general sense, anydisplay device capable of integration with a user input device (e.g.,touchscreen, bezel mounted interface, keyboard, mouse, trackpad, and thelike) is suitable for implementation in the present invention.

The user input device may include any user input device known in theart. For example, the user input device may include, but is not limitedto, a keyboard, a keypad, a touchscreen, a lever, a knob, a scrollwheel, a track ball, a switch, a dial, a sliding bar, a scroll bar, aslide, a handle, a touch pad, a paddle, a steering wheel, a joystick, abezel input device, or the like. In the case of a touchscreen interface,those skilled in the art should recognize that a large number oftouchscreen interfaces may be suitable for implementation in the presentinvention. For instance, the display device may be integrated with atouchscreen interface, such as, but not limited to, a capacitivetouchscreen, a resistive touchscreen, a surface acoustic basedtouchscreen, an infrared based touchscreen, or the like. In a generalsense, any touchscreen interface capable of integration with the displayportion of a display device is suitable for implementation in thepresent invention. In another embodiment, the user input device mayinclude, but is not limited to, a bezel mounted interface.

While embodiments of the present disclosure illustrate the controller202 may be coupled to the characterization tool 100 or integrated intothe characterization tool 100 as a component, the controller 202 is notan integral or required component of the characterization tool 100. Inaddition, while embodiments of the present disclosure illustrate a userinterface may be coupled to the controller 202 or integrated into thecontroller 202 as a component, the user interface is not an integral orrequired component of the controller 202 or the characterization tool100. Therefore, the above description should not be interpreted as alimitation on the scope of the present disclosure but merely anillustration.

In one embodiment, emissions from the electron beam emitters 106 of theelectron beam source array 102 are read back and/or processed by one ormore sets of electronics coupled to, and/or software stored on, thecontroller 202. In another embodiment, images generated by, or from asurface of, one or more components (e.g., electrostatic lenses,electromagnetic lenses, detectors 150, or the like) of theelectron-optical column 132 are read back and/or processed by one ormore sets of electronics coupled to, and/or software stored on, thecontroller 202.

In another embodiment, the stack of one or more positioners 116 areprecision-controlled via the controller 202. For example, the stack ofone or more positioners 116 may include one or morepiezoelectric-actuated positioners, or actuators. By way of anotherexample, the stack of one or more actuators 116 may be controlled viathe controller 202 to move via motion (e.g., motion measured insub-micron increments). In this regard, the stack of one or morepositioners 116 may adjusted from within the UHV environment, such thatminor adjustments necessary to offset deflection caused by an expandedemitter tip 108 when heated during operation of the SEM review tool 100may be made.

In another embodiment, the electron beam emitters 106 include anextractor aperture. In one example, the extractor driving voltages maybe independently set and/or calibrated for the electron beam emitters106. In another example, the electric current on each extractor may beindependently read and/or analyzed. The stack of the one or morepositioners 116 of a particular electron beam emitter 106 may scan thearea near the bore (e.g., hole or opening) of an electrostatic lensand/or electromagnetic lens in an electron-optical column 132 pairedwith the particular electron beam emitter 106. The electric currentgenerated by the electron beam at the bore may be measured via anelectrometer or amplifier communicatively coupled to the electrostaticlens and/or electromagnetic lens, while the stack of one or morepositioners 116 scans the bore and surrounding areas. The electrometeror amplifier may scan the lens image to find the bore via a coarsealignment process and/or via a fine alignment process. The one or morexyz-manipulators, or actuators, 126 may be adjusted via the outputgenerated from the coarse adjustment process and/or the stack of one ormore piezoelectric-actuated positioners, or actuators, 116 may beadjusted by on the output generated from the fine adjustment process.For instance, any of the one or more actuators 126 and/or the one ormore actuators 116 may be independently and precisely positioned. Inaddition, at least some of the one or more actuators 126 and/or the oneor more actuators 116 may be positioned as a set or group. It is notedherein the independent, precise positioning may occur while the sourceelectron beam array 102 is in a UHV environment and/or during operation.

In this regard, a position where the preferred (e.g., highest and/orpreviously predetermined) percentage of a generated electron beam passesthrough the paired electron-optical column 132 may be determined throughautomated analysis of the scanned positions and the measured current foreach position.

Although embodiments of the present disclosure are directed to the stackof one or more positioners 116 including electrically-driven actuators116, it is noted herein the positioners 116 may be mechanically-driven(e.g., via a push-pull assembly, a flexure assembly, or the like).Therefore, the above description should not be interpreted as alimitation on the scope of the present disclosure, but merely anillustration.

Although embodiments of the present disclosure are directed tocharacterization tool of the characterization system 200 as includingthe SEM review tool 100, it is noted herein the characterization tool ofthe characterization system 200 may include a FIB review tool or anoptical inspection tool. Therefore, the above description should not beinterpreted as a limitation on the scope of the present disclosure butmerely an illustration.

FIGS. 3A-3E generally illustrate a test chamber 300 coupled to the SEMreview tool 100, in accordance with one or more embodiments of thepresent disclosure.

In one embodiment, the test chamber 300 is a vacuum vessel capable ofoperating under an ultra-high vacuum (UHV) environment. In anotherembodiment, the test chamber 300 includes a housing 302. In anotherembodiment, the housing 302 includes a viewport 304. In anotherembodiment, the electron beams 152 generated by the electron beamemitters 106 of the electron beam sources 104 are visible through theviewport 304. For example, all electron beam emitters 106 may share thesame test chamber 300. In another embodiment, the viewport 304 may beutilized to inspect the electron beam sources 104. For example, one ormore imaging devices (e.g., camera, detector, pyrometer, vibrometer, orthe like) may be positioned in front of the viewport 304 (e.g., theviewport 304 is within a line of sight of the one or more imagingdevices). In this regard, the viewport 304 may be utilized to inspectthe electron beams 152 via one or more processes including, but notlimited to, visual inspection or calibration, pyrometry (e.g., thermalcalibration) or vibrometry. In addition, the electron beam sources 104may be adjusted to obtain a selected and/or predetermined temperature(or color) of the emitter tips 108 in the electron beam sources 104(e.g., set the temperature to meet a preferred length of life for theelectron beam source 104 before burn-out of the emitter tip 108) and/orto offset misalignment caused by the increased temperature of theemitter tips 108 in the electron beam sources 104 during operation.

In one example, the source tower 124 may be utilized when inspecting theelectron beams 152 through the viewport 304. As illustrated in FIG. 3B,the source tower 124 may raise the electron beam source array 102 fromthe electron-optical column array 130. As illustrated in FIGS. 3C-3E,the source tower 124 may lower each of the electron beam sources 104 infront of the viewport 304 to allow for inspection of the electron beam152, and then raise the electron beam source 104 back into positionfollowing inspection, in sequential order. Following inspection, thesource tower 124 may lower the electron beam source array 102 intoplace, with the kinematic mount assemblies 134 acting as guides. Eachelectron beam source 104 may be fine-adjusted via the coupled-to stackof one or more positioners 116. In this regard, the same position may berepeatedly achieved each time the electron beam source array 102 isdisengaged and re-engaged with the electron-optical column array 130. Inaddition, the electron beam emitters 106 may be coupled to theelectron-optical column 132 in a manner so as to ensure a preferredand/or predetermined dynamics performance (e.g., ensure a preferredand/or predetermined level of vibration).

FIG. 4A illustrates a process flow diagram depicting a method 400 forcalibrating electron beams 152 generated by the SEM review tool 100, inaccordance with one or more embodiments of the present disclosure. It isnoted herein the method 400 is not limited to the steps provided. Forexample, the method 400 may instead include more or fewer steps. By wayof another example, the method 400 may perform the steps in an orderother than provided. Therefore, the above description should not beinterpreted as a limitation on the scope of the present disclosure, butmerely an illustration.

In step 402, an area surrounding a bore of an electron-optical column isscanned for an electric current generated by an electron beam directedat the bore. In one embodiment, an electron beam emitter 106 of anelectron beam source 104 is paired with an electron-optical column 132of the electron-optical column array 130. In another embodiment, theelectron beam emitter 106 generates an electron beam 152 and directs itnear the bore of the electron-optical column 132. In another embodiment,the electron beam 152 is scanned across the area surrounding the bore ofthe electron-optical column 132. In another embodiment, the electriccurrent generated by the electron beam 152 is measured via anelectrometer.

In step 404, coarse adjustment data is determined from the electriccurrent measurements. In one embodiment, the coarse adjustment data iscalculated from the electric current measurements. In anotherembodiment, the coarse adjustment data is retrieved from stored datacorresponding to the electric current measurements. In step 406, thesource tower 124 (e.g., the one or more actuators 126 of the sourcetower 124) is adjusted (e.g., along an x-axis, a y-axis, and/or az-axis) via a coarse alignment process based on the coarse adjustmentdata.

In step 408, fine adjustment data is determined from the electriccurrent measurements. In one embodiment, the fine adjustment data iscalculated from the electric current measurements. In anotherembodiment, the fine adjustment data is retrieved from stored datacorresponding to the electric current measurements. In step 410, thestack of one or more positioners 116 is adjusted (e.g., along an x-axis,a y-axis, and/or a z-axis) via a fine alignment process based on thefine adjustment data.

In this regard, a preferred position (e.g., a position where the highestpercentage of a generated electron beam passes through the pairedelectron-optical column) may be determined through automated analysis ofthe scanned positions and the measured current for each position. Forexample, the preferred position may be determined within an UHVenvironment during operation of the SEM review tool 100.

FIG. 4B illustrates a process flow diagram depicting a method 420 forinspecting a source electron beam array 102 of the SEM review tool 100,in accordance with one or more embodiments of the present disclosure. Itis noted herein the method 420 is not limited to the steps provided. Forexample, the method 420 may instead include more or fewer steps. By wayof another example, the method 420 may perform the steps in an orderother than provided. Therefore, the above description should not beinterpreted as a limitation on the scope of the present disclosure, butmerely an illustration.

In step 422, the electron beam source array 102 is dismounted from theelectron-optical column array 130. In one embodiment, the kinematicmount assemblies 134 between the carrier plate 120 of the electron beamsource array 102 and the electron-optical column array 130 is uncoupled.In another embodiment, the source tower 124 raises the electron beamsource array 102.

In step 424, a first electron beam source 104 of the electron beamsource array 102 is aligned in front of the viewport 304 of the testchamber 300. In one embodiment, the first electron beam source 104 islowered in front of the viewport 304 during operation. In step 426, theelectron beam 152 generated by the first electron beam source 104 ismeasured and/or analyzed via one or more inspection processes. Forexample, the one or more inspection processes may include, but are notlimited to, optical inspection, pyrometry, vibrometry, or the like. Instep 428, the first electron beam source 104 of the electron beam sourcearray 102 is repositioned within the electron beam source array 102.

In step 430, at least an additional electron beam source 104 of theelectron beam source array 102 is aligned in front of the viewport 304of the test chamber 300. In one embodiment, the at least the additionalelectron beam source 104 is lowered in front of the viewport 304 duringoperation. In step 432, the electron beam 152 generated by the at leastthe additional electron beam source 104 is measured and/or analyzed viaone or more inspection processes. For example, the one or moreinspection processes may include, but are not limited to, opticalinspection, pyrometry, vibrometry, or the like. In step 434, the atleast the additional electron beam source 104 of the electron beamsource array 102 is repositioned within the electron beam source array102.

In step 436, the electron beam source array 102 is remounted on theelectron-optical column array 130. In one embodiment, the kinematicmount assemblies 134 between the carrier plate 120 of the electron beamsource array 102 and the electron-optical column array 130 are coupledtogether. In another embodiment, the source tower 124 repositions theelectron beam source array 102 via one or more coarse alignmentprocesses.

In step 434, the position of the electron beams 152 generated by theelectron beam source array 102 are adjusted based on data obtained viathe one or more inspection processes. In step 436, the electron beams152 generated by the electron beam source array 102 are aligned with theelectron-optical columns 132 of the electron-optical column array 130.In one embodiment, the electron beams 152 generated by the electron beamsource array 102 are aligned with the electron-optical columns 132 ofthe electron-optical column array 130 via one or more steps of method400.

Advantages of the present disclosure are directed to a multi-emitter,multi-column scanning electron microscopy (SEM) tool. Advantages of thepresent disclosure are also directed to wafer inspection or lithographyvia high brightness emission for each column in the multi-column SEMtool. Advantages of the present disclosure are also directed toautomated alignment of an electron beam through a column aperture orextractor bore of an electron-optical column. Advantages of the presentdisclosure are also directed to in-situ visual, thermal, and/orvibration inspection of individual or group electron beam sources withinan electron beam source array. Advantages of the present disclosure arealso directed to in-situ calibration of individual or group electronbeam sources within an electron beam source array.

Those having skill in the art will recognize that the state of the arthas progressed to the point where there is little distinction leftbetween hardware, software, and/or firmware implementations of aspectsof systems; the use of hardware, software, and/or firmware is generally(but not always, in that in certain contexts the choice between hardwareand software can become significant) a design choice representing costvs. efficiency tradeoffs. Those having skill in the art will appreciatethat there are various vehicles by which processes and/or systems and/orother technologies described herein can be effected (e.g., hardware,software, and/or firmware), and that the preferred vehicle will varywith the context in which the processes and/or systems and/or othertechnologies are deployed. For example, if an implementer determinesthat speed and accuracy are paramount, the implementer may opt for amainly hardware and/or firmware vehicle; alternatively, if flexibilityis paramount, the implementer may opt for a mainly softwareimplementation; or, yet again alternatively, the implementer may opt forsome combination of hardware, software, and/or firmware. Hence, thereare several possible vehicles by which the processes and/or devicesand/or other technologies described herein may be effected, none ofwhich is inherently superior to the other in that any vehicle to beutilized is a choice dependent upon the context in which the vehiclewill be deployed and the specific concerns (e.g., speed, flexibility, orpredictability) of the implementer, any of which may vary. Those skilledin the art will recognize that optical aspects of implementations willtypically employ optically-oriented hardware, software, and or firmware.

In some implementations described herein, logic and similarimplementations may include software or other control structures.Electronic circuitry, for example, may have one or more paths ofelectrical current constructed and arranged to implement variousfunctions as described herein. In some implementations, one or moremedia may be configured to bear a device-detectable implementation whensuch media hold or transmit device-detectable instructions operable toperform as described herein. In some variants, for example,implementations may include an update or modification of existingsoftware or firmware, or of gate arrays or programmable hardware, suchas by performing a reception of or a transmission of one or moreinstructions in relation to one or more operations described herein.Alternatively or in addition, in some variants, an implementation mayinclude special-purpose hardware, software, firmware components, and/orgeneral-purpose components executing or otherwise invokingspecial-purpose components. Specifications or other implementations maybe transmitted by one or more instances of tangible transmission mediaas described herein, optionally by packet transmission or otherwise bypassing through distributed media at various times.

Alternatively, or additionally, implementations may include executing aspecial-purpose instruction sequence or invoking circuitry for enabling,triggering, coordinating, requesting, or otherwise causing one or moreoccurrences of virtually any functional operations described herein. Insome variants, operational or other logical descriptions herein may beexpressed as source code and compiled or otherwise invoked as anexecutable instruction sequence. In some contexts, for example,implementations may be provided, in whole or in part, by source code,such as C++, or other code sequences. In other implementations, sourceor other code implementation, using commercially available and/ortechniques in the art, may be compiled/implemented/translated/convertedinto a high-level descriptor language (e.g., initially implementingdescribed technologies in C, C++, python, Ruby on Rails, Java, PHP,.NET, or Node.js programming language and thereafter converting theprogramming language implementation into a logic-synthesizable languageimplementation, a hardware description language implementation, ahardware design simulation implementation, and/or other such similarmode(s) of expression). For example, some or all of a logical expression(e.g., computer programming language implementation) may be manifestedas a Verilog-type hardware description (e.g., via Hardware DescriptionLanguage (HDL) and/or Very High Speed Integrated Circuit HardwareDescriptor Language (VHDL)) or other circuitry model which may then beused to create a physical implementation having hardware (e.g., anApplication Specific Integrated Circuit). Those skilled in the art willrecognize how to obtain, configure, and optimize suitable transmissionor computational elements, material supplies, actuators, or otherstructures in light of these teachings.

The foregoing detailed description has set forth various embodiments ofthe devices and/or processes via the use of block diagrams, flowcharts,and/or examples. Insofar as such block diagrams, flowcharts, and/orexamples contain one or more functions and/or operations, it will beunderstood by those within the art that each function and/or operationwithin such block diagrams, flowcharts, or examples can be implemented,individually and/or collectively, by a wide range of hardware, software,firmware, or virtually any combination thereof. In one embodiment,several portions of the subject matter described herein may beimplemented via Application Specific Integrated Circuits (ASICs), FieldProgrammable Gate Arrays (FPGAs), digital signal processors (DSPs), orother integrated formats. However, those skilled in the art willrecognize that some aspects of the embodiments disclosed herein, inwhole or in part, can be equivalently implemented in integratedcircuits, as one or more computer programs running on one or morecomputers (e.g., as one or more programs running on one or more computersystems), as one or more programs running on one or more processors(e.g., as one or more programs running on one or more microprocessors),as firmware, or as virtually any combination thereof, and that designingthe circuitry and/or writing the code for the software and or firmwarewould be well within the skill of one of skill in the art in light ofthis disclosure. In addition, those skilled in the art will appreciatethat the mechanisms of the subject matter described herein are capableof being distributed as a program product in a variety of forms, andthat an illustrative embodiment of the subject matter described hereinapplies regardless of the particular type of signal bearing medium usedto actually carry out the distribution. Examples of a signal bearingmedium include, but are not limited to, the following: a recordable typemedium such as a floppy disk, a hard disk drive, a Compact Disc (CD), aDigital Video Disk (DVD), a digital tape, a computer memory, etc.; and atransmission type medium such as a digital and/or an analogcommunication medium (e.g., a fiber optic cable, a waveguide, a wiredcommunications link, a wireless communication link (e.g., transmitter,receiver, transmission logic, reception logic, etc.), etc.).

In a general sense, those skilled in the art will recognize that thevarious embodiments described herein can be implemented, individuallyand/or collectively, by various types of electro-mechanical systemshaving a wide range of electrical components such as hardware, software,firmware, and/or virtually any combination thereof; and a wide range ofcomponents that may impart mechanical force or motion such as rigidbodies, spring or torsional bodies, hydraulics, electro-magneticallyactuated devices, and/or virtually any combination thereof.Consequently, as used herein “electro-mechanical system” includes, butis not limited to, electrical circuitry operably coupled with atransducer (e.g., an actuator, a motor, a piezoelectric crystal, a MicroElectro Mechanical System (MEMS), etc.), electrical circuitry having atleast one discrete electrical circuit, electrical circuitry having atleast one integrated circuit, electrical circuitry having at least oneapplication specific integrated circuit, electrical circuitry forming ageneral purpose computing device configured by a computer program (e.g.,a general purpose computer configured by a computer program which atleast partially carries out processes and/or devices described herein,or a microprocessor configured by a computer program which at leastpartially carries out processes and/or devices described herein),electrical circuitry forming a memory device (e.g., forms of memory(e.g., random access, flash, read only, etc.)), electrical circuitryforming a communications device (e.g., a modem, communications switch,optical-electrical equipment, etc.), and/or any non-electrical analogthereto, such as optical or other analogs. Those skilled in the art willalso appreciate that examples of electro-mechanical systems include butare not limited to a variety of consumer electronics systems, medicaldevices, as well as other systems such as motorized transport systems,factory automation systems, security systems, and/orcommunication/computing systems. Those skilled in the art will recognizethat electro-mechanical as used herein is not necessarily limited to asystem that has both electrical and mechanical actuation except ascontext may dictate otherwise.

In a general sense, those skilled in the art will recognize that thevarious aspects described herein which can be implemented, individuallyand/or collectively, by a wide range of hardware, software, firmware,and/or any combination thereof can be viewed as being composed ofvarious types of “electrical circuitry.” Consequently, as used herein“electrical circuitry” includes, but is not limited to, electricalcircuitry having at least one discrete electrical circuit, electricalcircuitry having at least one integrated circuit, electrical circuitryhaving at least one application specific integrated circuit, electricalcircuitry forming a general purpose computing device configured by acomputer program (e.g., a general purpose computer configured by acomputer program which at least partially carries out processes and/ordevices described herein, or a microprocessor configured by a computerprogram which at least partially carries out processes and/or devicesdescribed herein), electrical circuitry forming a memory device (e.g.,forms of memory (e.g., random access, flash, read only, etc.)), and/orelectrical circuitry forming a communications device (e.g., a modem,communications switch, optical-electrical equipment, etc.). Those havingskill in the art will recognize that the subject matter described hereinmay be implemented in an analog or digital fashion or some combinationthereof.

Those skilled in the art will recognize that at least a portion of thedevices and/or processes described herein can be integrated into a dataprocessing system. Those having skill in the art will recognize that adata processing system generally includes one or more of a system unithousing, a video display device, memory such as volatile or non-volatilememory, processors such as microprocessors or digital signal processors,computational entities such as operating systems, drivers, graphicaluser interfaces, and applications programs, one or more interactiondevices (e.g., a touch pad, a touch screen, an antenna, etc.), and/orcontrol systems including feedback loops and control motors (e.g.,feedback for sensing position and/or velocity; control motors for movingand/or adjusting components and/or quantities). A data processing systemmay be implemented utilizing suitable commercially available components,such as those typically found in data computing/communication and/ornetwork computing/communication systems.

One skilled in the art will recognize that the herein describedcomponents (e.g., operations), devices, objects, and the discussionaccompanying them are used as examples for the sake of conceptualclarity and that various configuration modifications are contemplated.Consequently, as used herein, the specific exemplars set forth and theaccompanying discussion are intended to be representative of their moregeneral classes. In general, use of any specific exemplar is intended tobe representative of its class, and the non-inclusion of specificcomponents (e.g., operations), devices, and objects should not be takenlimiting.

Although a user is described herein as a single figure, those skilled inthe art will appreciate that the user may be representative of a humanuser, a robotic user (e.g., computational entity), and/or substantiallyany combination thereof (e.g., a user may be assisted by one or morerobotic agents) unless context dictates otherwise. Those skilled in theart will appreciate that, in general, the same may be said of “sender”and/or other entity-oriented terms as such terms are used herein unlesscontext dictates otherwise.

With respect to the use of substantially any plural and/or singularterms herein, those having skill in the art can translate from theplural to the singular and/or from the singular to the plural as isappropriate to the context and/or application. The varioussingular/plural permutations are not expressly set forth herein for sakeof clarity.

The herein described subject matter sometimes illustrates differentcomponents contained within, or connected with, different othercomponents. It is to be understood that such depicted architectures aremerely exemplary, and that in fact many other architectures may beimplemented which achieve the same functionality. In a conceptual sense,any arrangement of components to achieve the same functionality iseffectively “associated” such that the desired functionality isachieved. Hence, any two components herein combined to achieve aparticular functionality can be seen as “associated with” each othersuch that the desired functionality is achieved, irrespective ofarchitectures or intermedial components. Likewise, any two components soassociated can also be viewed as being “operably connected”, or“operably coupled,” to each other to achieve the desired functionality,and any two components capable of being so associated can also be viewedas being “operably couplable,” to each other to achieve the desiredfunctionality. Specific examples of operably couplable include but arenot limited to physically mateable and/or physically interactingcomponents, and/or wirelessly interactable, and/or wirelesslyinteracting components, and/or logically interacting, and/or logicallyinteractable components.

In some instances, one or more components may be referred to herein as“configured to,” “configurable to,” “operable/operative to,”“adapted/adaptable,” “able to,” “conformable/conformed to,” etc. Thoseskilled in the art will recognize that such terms (e.g., “configuredto”) can generally encompass active-state components and/orinactive-state components and/or standby-state components, unlesscontext requires otherwise.

While particular aspects of the present subject matter described hereinhave been shown and described, it will be apparent to those skilled inthe art that, based upon the teachings herein, changes and modificationsmay be made without departing from the subject matter described hereinand its broader aspects and, therefore, the appended claims are toencompass within their scope all such changes and modifications as arewithin the true spirit and scope of the subject matter described herein.It will be understood by those within the art that, in general, termsused herein, and especially in the appended claims (e.g., bodies of theappended claims) are generally intended as “open” terms (e.g., the term“including” should be interpreted as “including but not limited to,” theterm “having” should be interpreted as “having at least,” the term“includes” should be interpreted as “includes but is not limited to,”etc.). It will be further understood by those within the art that if aspecific number of an introduced claim recitation is intended, such anintent will be explicitly recited in the claim, and in the absence ofsuch recitation no such intent is present. For example, as an aid tounderstanding, the following appended claims may contain usage of theintroductory phrases “at least one” and “one or more” to introduce claimrecitations. However, the use of such phrases should not be construed toimply that the introduction of a claim recitation by the indefinitearticles “a” or “an” limits any particular claim containing suchintroduced claim recitation to claims containing only one suchrecitation, even when the same claim includes the introductory phrases“one or more” or “at least one” and indefinite articles such as “a” or“an” (e.g., “a” and/or “an” should typically be interpreted to mean “atleast one” or “one or more”); the same holds true for the use ofdefinite articles used to introduce claim recitations. In addition, evenif a specific number of an introduced claim recitation is explicitlyrecited, those skilled in the art will recognize that such recitationshould typically be interpreted to mean at least the recited number(e.g., the bare recitation of “two recitations,” without othermodifiers, typically means at least two recitations, or two or morerecitations). Furthermore, in those instances where a conventionanalogous to “at least one of A, B, and C, etc.” is used, in generalsuch a construction is intended in the sense one having skill in the artwould understand the convention (e.g., “ a system having at least one ofA, B, and C” would include but not be limited to systems that have Aalone, B alone, C alone, A and B together, A and C together, B and Ctogether, and/or A, B, and C together, etc.). In those instances where aconvention analogous to “at least one of A, B, or C, etc.” is used, ingeneral such a construction is intended in the sense one having skill inthe art would understand the convention (e.g., “ a system having atleast one of A, B, or C” would include but not be limited to systemsthat have A alone, B alone, C alone, A and B together, A and C together,B and C together, and/or A, B, and C together, etc.). It will be furtherunderstood by those within the art that typically a disjunctive wordand/or phrase presenting two or more alternative terms, whether in thedescription, claims, or drawings, should be understood to contemplatethe possibilities of including one of the terms, either of the terms, orboth terms unless context dictates otherwise. For example, the phrase “Aor B” will be typically understood to include the possibilities of “A”or “B” or “A and B.

With respect to the appended claims, those skilled in the art willappreciate that recited operations therein may generally be performed inany order. Also, although various operational flows are presented in asequence(s), it should be understood that the various operations may beperformed in other orders than those which are illustrated, or may beperformed concurrently. Examples of such alternate orderings may includeoverlapping, interleaved, interrupted, reordered, incremental,preparatory, supplemental, simultaneous, reverse, or other variantorderings, unless context dictates otherwise. Furthermore, terms like“responsive to,” “related to,” or other past-tense adjectives aregenerally not intended to exclude such variants, unless context dictatesotherwise.

Although particular embodiments of this invention have been illustrated,it is apparent that various modifications and embodiments of theinvention may be made by those skilled in the art without departing fromthe scope and spirit of the foregoing disclosure. It is believed thatthe present disclosure and many of its attendant advantages will beunderstood by the foregoing description, and it will be apparent thatvarious changes may be made in the form, construction and arrangement ofthe components without departing from the disclosed subject matter orwithout sacrificing all of its material advantages. The form describedis merely explanatory, and it is the intention of the following claimsto encompass and include such changes. Accordingly, the scope of theinvention should be limited only by the claims appended hereto.

What is claimed:
 1. A scanning electron microscopy (SEM) system,comprising: an electron-optical column array comprising a plurality ofelectron-optical columns; and an electron beam source array couplable tothe electron-optical column array, wherein the electron beam sourcearray comprises: a plurality of electron beam sources configured togenerate a plurality of electron beams, wherein at least some of theelectron beam sources comprise: an emitter coupled to an emitter holder,wherein the emitter includes one or more emitter tips configured togenerate one or more electron beams of the plurality of electron beams;and a stack of one or more positioners coupled to the emitter holder,wherein the stack of one or more positioners is configured to adjust aposition of the emitter based on one or more measurements of theelectron beam generated by the emitter, wherein the emitter isconfigured to scan the one or more electron beams across an areasurrounding a bore of a particular electron-optical column of theplurality of electron-optical columns; a carrier plate coupled to theplurality of electron beam sources; and a source tower coupled to thecarrier plate, wherein the source tower is configured to adjust aposition of the plurality of electron beam sources relative to aposition of the plurality of electron-optical columns.
 2. The system inclaim 1, wherein the emitter is configured to receive voltage via avoltage terminal coupled to the emitter holder.
 3. The system in claim2, wherein the emitter includes two or more emitter tips configured toreceive voltage via the voltage terminal coupled to the emitter holder.4. The system in claim 3, wherein at least a second emitter tip of thetwo or more emitter tips is configured to receive a selected amount ofelectric current when a first emitter tip of the two or more emittertips fails.
 5. The system in claim 1, wherein the at least some of theplurality of electron beam sources comprise: a thermal bypass, whereinthe thermal bypass is positioned between the emitter holder and thestack of one or more positioners, wherein the thermal bypass ispositioned between the stack of one or more positioners and the carrierplate, wherein the thermal bypass is configured to transfer heat fromthe emitter holder to the carrier plate.
 6. The system in claim 1,wherein the electron beam source array comprises: a magnetic shield,wherein the magnetic shield surrounds the plurality of electron beamsources, wherein the carrier plate is coupled to the magnetic shield,wherein the source tower is coupled to the magnetic shield.
 7. Thesystem in claim 6, wherein the source tower is coupled to the magneticshield via a flexible joint.
 8. The system in claim 1, wherein theelectron-optical element comprises at least one of an electrostatic lensor an electromagnetic lens.
 9. The system in claim 1, comprising acontroller, wherein the controller includes one or more processorsconfigured to receive one or more images from a characterization tool,wherein the controller includes memory configured to store a set ofprogram instructions, wherein the one or more processors are configuredto execute the set of program instructions.
 10. The system in claim 9,wherein the stack of one or more positioners includes one or moreactuators, wherein the one or more actuators are configured to adjustthe position of the emitter based on the one or more measurements of theelectron beam generated by the emitter.
 11. The system in claim 10,wherein the controller is configured to adjust one or more actuators arevia one or more automated adjustment processes.
 12. The system in claim9, wherein the source tower includes one or more actuators, wherein theone or more actuators are configured to adjust the position of theplurality of electron beam sources relative to the position of theplurality of electron-optical columns.
 13. The system in claim 12,wherein the controller is configured to adjust one or more actuators arevia one or more automated adjustment processes.
 14. The system in claim1, wherein at least one of the electron beam source array or theelectron-optical column array includes one or more components fabricatedfrom ultra-high vacuum (UHV) environment-compliant materials.
 15. Thesystem in claim 14, wherein the electron beam source array and theelectron-optical column array share a UHV environment.
 16. The system inclaim 1, further comprising: one or more kinematic mount assemblies,wherein the electron beam source array is couplable to theelectron-optical column array via the one or more kinematic mountassemblies.
 17. The system in claim 16, wherein the source tower isconfigured to adjust a position of the plurality of electron beamsources relative to a position of the plurality of electron-opticalcolumns based on feedback from the one or more kinematic mountassemblies.
 18. The system in claim 16, wherein the one or morekinematic mount assemblies include one or more safety switches.
 19. Thesystem in claim 18, wherein the source tower is configured to adjust aposition of the plurality of electron beam sources relative to aposition of the plurality of electron-optical columns based on feedbackfrom the one or more safety switches.
 20. The system in claim 16,wherein the carrier plate of the electron beam source array is couplableto the electron-optical column array via the one or more kinematic mountassemblies.
 21. The system in claim 1, comprising a test chamber,wherein at least some of the plurality of electron beams are inspectablevia a viewport of the test chamber.
 22. The system in claim 21,comprising an inspection device, wherein the inspection device isconfigured to sequentially inspect the at least some of the plurality ofelectron beams via the viewport in the test chamber.
 23. The system inclaim 22, wherein the inspection device is configured to sequentiallyinspect the at least some of the plurality of electron beams via theviewport in the test chamber while the electron beam source array isdismounted from the electron-optical column array.
 24. A scanningelectron microscopy (SEM) system, comprising: an electron-optical columnarray comprising a plurality of electron-optical columns; and anelectron beam source array couplable to the electron-optical columnarray, wherein the electron beam source array comprises a plurality ofelectron beam sources configured to generate a plurality of electronbeams, wherein at least some of the electron beam sources comprise: anemitter coupled to an emitter holder, wherein the emitter includes oneor more emitters tips configured to generate one or more electron beamsof the plurality of electron beams; a stack of one or more actuatorscoupled to the emitter holder, wherein the stack of one or moreactuators is configured to adjust a position of the emitter; and athermal bypass, wherein the thermal bypass is positioned between theemitter holder and the stack of one or more positioners, wherein thethermal bypass is positioned between the stack of one or morepositioners and the carrier plate, wherein the thermal bypass isconfigured to transfer heat from the emitter holder to the carrierplate.
 25. A scanning electron microscopy (SEM) system, comprising: anelectron-optical column array comprising a plurality of electron-opticalcolumns; and an electron beam source array couplable to theelectron-optical column array, the electron beam source array comprisinga plurality of electron beam sources configured to generate a pluralityof electron beams, wherein at least some of the electron beam sourcescomprise an emitter, wherein the emitter includes a first emitter tipconfigured to generate a first electron beam of the plurality ofelectron beams and a second emitter tip configured to generate a secondelectron beam of the plurality of electron beams, wherein the secondemitter tip is configured to receive a selected amount of electriccurrent when the first emitter tip fails.
 26. A method, comprising:scanning an area surrounding a bore of an electron-optical element of anelectron-optical column for an electric current generated by an electronbeam directed at the bore, wherein the electron-optical column is acomponent of an electron-optical column array; determining coarseadjustment data based on the scanned electric current; providing thecoarse adjustment data to adjust a source tower of an electron beamsource array via one or more coarse alignment processes; determiningfine adjustment data based on the scanned electric current; andproviding the fine adjustment data to adjust one or more positionerscoupled to an electron beam source of the electron beam source array viaone or more fine alignment processes, wherein at least one of theelectron-optical column array or the electron beam source array is acomponent of a scanning electron microscopy (SEM) system.
 27. A method,comprising: dismounting an electron beam source array from anelectron-optical column array, wherein the electron beam source arrayincludes a plurality of electron beam sources, wherein the plurality ofelectron beam sources generates a plurality of electron beams; aligninga first electron beam source of the plurality of electron beam sourceswith a viewport of a test chamber, wherein the first electron beamsource generates a first electron beam of the plurality of electronbeams; performing one or more inspection processes on the first electronbeam of the plurality of electron beams; repositioning the firstelectron beam source within the electron beam source array; aligning atleast an additional electron beam source of the electron beam sourcearray with the viewport of the test chamber, wherein the at least theadditional electron beam source generates at least an additionalelectron beam of the plurality of electron beams; performing one or moreinspection processes on the at least the additional electron beam of theplurality of electron beams; repositioning the at least the additionalelectron beam source within the electron beam source array; andremounting the electron beam source array onto the electron-opticalcolumn array, wherein at least one of the electron beam source array,the electron-optical column array, or the test chamber is a component ofa scanning electron microscopy (SEM) system.
 28. The method in claim 27,wherein the one or more inspection processes performed on at least oneof the first electron beam or the at least the additional electron beamincludes: at least one of one or more optical inspection processes, oneor more pyrometry processes, or one or more vibrometry processes. 29.The method in claim 27, further comprising: adjusting at least some ofthe plurality of electron beams based on data obtained via at least oneof the one or more inspection processes performed on the first electronbeam or the one or more inspection processes performed on the at leastthe additional electron beam.
 30. The method in claim 27, furthercomprising: aligning the plurality of electron beams generated by theplurality of electron beam sources of the electron beam source arraywith a plurality of electron-optical columns of the electron-opticalcolumn array
 31. The method in claim 30, wherein the aligning theplurality of electron beams generated by the plurality of electron beamsources of the electron beam source array with a plurality ofelectron-optical columns of the electron-optical column array furthercomprises: scanning an area surrounding a bore of an electron-opticalelement of an electron-optical column of the plurality ofelectron-optical columns for an electric current generated by anelectron beam of the plurality of electron beams directed at the bore.32. The method in claim 31, wherein the aligning the plurality ofelectron beams generated by the plurality of electron beam sources ofthe electron beam source array with a plurality of electron-opticalcolumns of the electron-optical column array further comprises:determining coarse adjustment data based on the scanned electriccurrent.
 33. The method in claim 32, wherein the aligning the pluralityof electron beams generated by the plurality of electron beam sources ofthe electron beam source array with a plurality of electron-opticalcolumns of the electron-optical column array further comprises:providing the coarse adjustment data to adjust a source tower of theelectron beam source array via one or more coarse alignment processes.34. The method in claim 33, wherein the aligning the plurality ofelectron beams generated by the plurality of electron beam sources ofthe electron beam source array with a plurality of electron-opticalcolumns of the electron-optical column array further comprises:determining fine adjustment data based on the scanned electric current.35. The method in claim 34, wherein the aligning the plurality ofelectron beams generated by the plurality of electron beam sources ofthe electron beam source array with a plurality of electron-opticalcolumns of the electron-optical column array further comprises:providing the fine adjustment data to adjust one or more positionerscoupled to an electron beam source of the plurality of electron beamsources of the electron beam source array via one or more fine alignmentprocesses.